Perhaps you should try some spelling variations:
"using java core snippets" » "using data core snippets"
"duong thi trac snippets" » "luong thi trac snippets", "dang thi trac snippets", "duong thi tran snippets", "duong thi tac snippets", "duong thi trang snippets"
"locating bug code snippets" » "locating bung code snippets", "locating bugs code snippets"

Try widening your search to All Fields.

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: (((("using java core snippets") or ("duong thi trac snippets"))) or ("locating bug code snippets"))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (((("using java core snippets") OR ("duong thi trac snippets"))) OR ("locating bug code snippets")).
• Removing quotes may allow a broader search: (((( using java core snippets ) or ( duong thi trac snippets ))) or ( locating bug code snippets )).
• Adding a wildcard symbol may retrieve word variants: (((("using java core snippets") or ("duong thi trac snippets"))) or ("locating bug code snippets"))*.